Three of my favourite Thai restaurants are Thai Metro, Siam Central and Busaba Ethai. Thai Metro and Siam Central are two sister restaurants near Goodge Street and Busaba Ethai is a well-known restaurant chain.
My personal favourite is Thai Metro and Siam Central is their Drunken Noodles, Drunken Fried Rice and their Tom Yum soup. I absolutely love their Drunken dishes! But I should also mention that it is quite spicy and not for the faint hearted.
Busaba Ethai is a popular Thai restaurant. Their menus are seasonal but all their dishes are generally quite nice. Their curries are spicy and full of flavour, their whole fried fish dishes are fresh, crispy and a delight to eat and their calamari and pandan chicken starters are definitely worth the price!